I guess it all depends on what u want to do with your airboat.
the simplicity of having 1 mag and only 6 plugs to worry about is a huge plus to me. I use my boat to hunt/frog and it gets treated accordingly. I love my gpu.
just me, but i'd get better pistons before another mag. and it would take a lot to make me do anything.

jopete wrote:I guess it all depends on what u want to do with your airboat.
the simplicity of having 1 mag and only 6 plugs to worry about is a huge plus to me. I use my boat to hunt/frog and it gets treated accordingly. I love my gpu.
just me, but i'd get better pistons before another mag. and it would take a lot to make me do anything.

good luck whatever u choose.

I already got 535133 pistons in it. Boat runs good. Just battling the typical oil usage of a GPU. I love my motor too. I hear going to pacemaker is like night and day. My thought behind it is if I do go that route in the future I'll already had it set up for a second plug. Why not add it.

Well, I can tell you, i ran against a guy in my boat with one mag off by mistake and he got me by a boat, ran same boat again with both mags on and jumped him out of the hole and walked away 4-5 boats ahead.
Also having 2 mags has the advantage of getting back to the ramp or camp should one mag die.
I built a setup that bolted in place of removed valve cover that drilled and counterbored cylinder head for bottom plug hole with engine assembled, plus a fixture that drilled for drive gear pin in the case with engine assembed, those tools are at Don 's in homestead.

Dual Mags will not produce any more power than a single mag. With dual mags you must reduce the timing to 25 degrees. Doing this and switching one mag off drops your timing to 20 degrees. This is proven by studying the RATE OF COMBUSTION. It takes longer for the fuel to burn all the way across the cylinder with one mag allowing you to run 30 degrees timing.
When running dual mags, the fuel burn has to meet in the middle of the cylinder so they have to be timed perfect. If not timed perfect, the plug that fires first burns all the fuel and the second spark burns nothing leaving you with the power of timing of 20 degrees.
1. One Mag motors may be up to 30 lbs less weight than dual mag motors.
2. Racers try to get as much timing as possible without creating detonation.
3. Dual mags are a must when running exotic fuels and nitrous. Also when installed in airplanes.
4. For the best power gain, try 3 into 1 tuned headers with the down tubes 30 to 32 inches long, merge collector and 2.25 muffler. pick up 14 to 20 more HP.
Note: if I were running 520 jugs, I would run one mag and plug the bottom spark plug holes. Set the timing at 30 degrees.

You might check into E-Mag. It is an electronic ignition set up that replaces the mag. Shouldn't cost much more than adding a mag but should give you way better performance than mags. The E-mag produces it's own power once the engine is running and is designed to run with automotive spark plugs and harness. They even have a hand propping option if that is a concern. It could replace the existing mag or be added. There have been some great reviews in the aviation side about them.